Antenna for mobile communications



Nov. 29, 1955 w. DARLING 2,725,473

ANTENNA FOR MOBILE COMMUNICATIONS Filed Oct. 26. 1951 .ag/24, @my

United States Patent Oilicc 2,725,473 Patented Nov. 29, 1955 ANTENNA FOR MOBILE COMlVIUNICATIONS Woodrow Darling, Merchantville, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application October 26, 1951, Serial No. 253,348 7 Claims. (Cl. 343-828) This invention relates to improvements in an electric antenna and more particularly to an electric antenna for mobile communications. l

Presently employed antennas, the so-called whip antennas, for police band frequencies of 152-162 mc. usually comprise a quarter wave conductor mounted vertically in the center of the car roof. At 150 mc. a quarter wave length is approximately 18 inches and, therefore, the effective height of such an antenna is (2/1r) 18 inches, or 11.5 inches so that the received signal is approximately one third field strength per meter.

As is well known in mobile transmitters, the radio frequency transmitting power is costly in terms of transmitter cost and high battery drain, and to double the power of a mobile transmitter will add approximately 25% to the cost of installation.

One of the objects of my invention is to provide an antenna for mobile communications in which the radio frequency transmitting power can be increased without substantialincrease in the cost of installation, and which is characterized by a substantially constant load impedance over an appreciable frequency range.

-A further aim of my invention is to provide an antenna for mobile communications in which the radio frequency transmitting power will be increased without substantially increasing the cost in terms of transmitter cost and high battery drain.

Another purpose of my invention is to provide an easily manufactured and easily installed electric antenna for mobile communications in which the power pattern in a horizontal plane and the gain has been improved over similar mobile antennas.

In general, my invention provides what is commonly termed a folded antenna for mobile communications which overcomes the objections of so-called whip antennas as set forth above, comprising a base fed halfwave length radiator coupled to a quarter wave length radiator by means of a non-radiating section, and a means for supporting said antenna.

Referring continuously to the drawing forming a part of my application:

Figure l is an elevation of my antenna with a coupling coil shown mounted on a base;

Figure 2 is a cross-section of the non-radiating section of my antenna taken along the line 2 2 of Figure l.

Figure 3 shows the horizontal pattern on the so-called whip antenna of one-quarter wave length and for comparison therewith, the power pattern of my improved antenna; and

Figure 4 shows the standing wave ratio of my improved antenna.

According to the present invention, my antenna consists of a top radiating section, 10, which is a conductor of one-half wave length fed at the base, a second or bottom radiating section, 16, which is a conductor of one-quarter wave length also fed at the base, and a nonradiating section 14, physically and electrically coupling the two radiating sections together.

Such non-radiating v,section can be formed in various ways. One way is to fold a portion of the antenna twice upon itself so as to produce a triangle in crosssection, the physical length of which is approximately onesixth wave length, less the length consumed in the folding. Another way is by folding a separate conductor of one-half `wave length in the same manner and connecting Vit to the two radiator sections by welding or the like.

As can be seen from Figure 2, the legs or elements, 11, 12, 13, of the non-radiating section of my antenna form the leg, which feeds the base of. radiator, 10, being further from the adjoining legs of the fold than is the leg, 13, connected to be fed by radiator, 16. This folded non-radiating section not only provides a physical separation of the two radiators but also provides phase shift so that the top and bottom radiators are additive in a horizontal plane thereby increasing the gain. Moreover, it controls the distribution of energy between the top and bottom radiators.

The driving generator (not shown) is connected to the base ofthe one quarter wave length radiator through a feed line, 18.

A typical installation is shown in Figure l, wherein my antenna is illustrated as being mounted on an upright supportingrod, 20, having ground rods, 22, and spring, 24, separated'from the antenna by an insulator, 26. Said ground rods are horizontally disposed and elevated above the base, 28, such asA a car trunk, on which the antenna is mounted, by a distance of onequarter wave length in order that the ground rods will be maintained above all other obstacles such as a car roof.' It fcan'be seen that the length of the supporting rod, 20, willfbe determined by the height of the surrounding obstacles.

The power pattern of the aforesaid typical installation of my folded antenna as compared with power pattern of a similar roof whip antenna is illustrated by Figure 3, wherein the reference numerals, A and B, designate the power patterns of my antenna and of a whip antenna,

respectively. It can clearly be seen that the power pat-v tern of my folded antenna is substantially greater than the power of the whip type antenna. Actual calcula@ tions show the average increase in gain to be l2.2.

Fig. 4 shows the standing wave ratio C of my folded antenna from which it will be seen that it has a constant load impedance over a wide frequency range. Actual tests of my antenna were made in the frequency range of 3000 mcs., but it will be understood that my invention is in no way limited to such range.

Although one form of my invention has been described in detail, it will be apparent that variations and changes may be made therein without departing from the spirit and scope thereof as outlined in the appended claims.

I claim:

l. An improved antenna for mobile communications having a first radiating section of one-half wave length of the operating frequency, a non-radiating section connected to one end of the lirst radiating section to feed energy thereto, said non-radiating section comprising three parallel joined sections each being one-sixth ot' a wave length of the operating frequency, and a second radiating section connected at one end to the other end of said non-radiating section to feed energy thereto, two of said sections being in a plane different from the other of said sections.

2. An improved antenna for mobile communications comprising a first base fed one-half wave length radiating section, a second base fed one-quarter wave length radiating section and a non-radiating section having three legs of Substantially one-sixth wave length and forming a triangle in cross-section, one leg of which is connected to the first radiating section, and another leg of which is connected to the top of the secondradiatingV section whereby energy is transferred from the second radiating section to the rst radiating section in 180 out of phase relation.

3. An improved antenna for mobile communications comprising a first radiating section of one-half wave length, a second radiating section of one-quarter Wave length, a non-radiating section coupling one end of said one-half wave length radiating section to an end of said onequarter wave length radiating section, said nonradiating section having three legs each of which is of substantially one sixth wave length, said legs in cross section forming the vertices of a triangle and providing radiation phase shift of 180 so that the radiations of the two radiators are additive in the horizontal plane, and a driving generator to feed energy to said rst radiator.

4. An improved antenna for mobile communications comprising a first radiating ysection of one-half Wave length fed at one end, a second radiating section of onequarter wave length fed at one end, a non-radiating section having three parallel legs of one-sixth wave length ioined by reverse loops, two of said legs lying in a plane different from the other of said legs one of said legs connected to one end of the rst radiator and an other of said legs connected to the second end of the second radiator whereby energy from second radiator transferred out of phase to the first radiator so that the radiations are additive in a horizontal plane, means to support said radiator, and a driving generator connected to the rst mentioned end of. the second radiator to feed energy to said second radiator.

5. An improved antenna for mobile communications having a irst radiating section of substantially One-half of a wavelength of the operating frequency, a second radiating section of substantially one-quarter of a wavelength of such frequency, and non-radiating section, comprising three parallel joined sections, two of said sections being in a plane different from the other of said sections and each being substantially one-sixth of a wavelength of such frequency, the said non-radiating section physically and electrically coupling the two radiating sections together.

6. An improved antenna for mobile communications comprising a first radiator of one-half wavelength of the operating frequency, a second radiator of one-quarter wavelength of the operating frequency, and a non-radiator connected at one end of said first radiator, and at the other end to an end of said second radiator, said non-radiator comprising three parallel sections, two of said sections being in a plane different from the other of said sections, said non-radiator having an inversely folded length of substantially one-sixth wavelength of the operating frequency and providing a physical separation and electrical connection of said radiators.

7. An improved antenna for mobile communications comprising a base fed one-half wavelength radiating section, a base fed one-quarter wavelength radiating section, and a base fed non-radiating section comprising three sections joined by reverse loops and connected between the base of said one-half wavelength radiating section and the top of said one-quarter wavelength radiating section whereby energy is fed from the onequarter wavelength radiating section to the one-half wavelength radiating section 180 degrees out of phase relation, two of the sections of said non-radiating section lying in a plane different from the other section of said non-radiating sections.

References Cited in the tile of this patent UNITED STATES PATENTS 1,914,886 Franklin June 20, 1933 1,957,949 Franklin et al. May 8, 1934 2,237,779 Carter Apr. 8, 1941 2,380,333 Scheldorf July 10, 1945 

